net: xilinx: emaclite: add minimal ndo_do_ioctl hook

This hook only implements a minimal set of ioctl hooks to be able to access
MII regs by using phytool.
When using this simple MAC controller, it's pretty difficult to do
debugging of the PHY chip without checking MII regs.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>